In an electronic device for use in GSM and WCDMA communications, the multimode engine has a duplexer to feed WCDMA transmit and receive paths to a WCDMA antenna, and a dedicated GSM antenna/switch module is used for the GSM modes, as shown in FIG. 1. In this dual antenna topology, no antenna switching is required between GSM and WCDMA modes. As shown, the GSM antenna switch is used for selection between four GSM receive paths and two GSM transmit paths. The duplexer only handles one WCDMA receive path and one WCDMA transmit path.
If more than one WCDMA or CDMA band is required in addition to the quad-band GSM bands, the complexity of the RF front-end increases significantly. For example, when the same antenna is used to support two CDMA bands (850 and 1900), a diplexer filter is used, along with two duplexers, to route the transmit paths and receive paths to the CDMA antenna, as shown in FIG. 2. As shown in FIG. 2, no switching is used for the CDMA bands. The use of a diplexer or passive matching of filters is generally feasible only when the frequency separation between the duplexers is sufficiently large, such as the frequency separation of 1 GHz. For example, it is not feasible to use a diplexer approach to combine a 1900 duplexer and a 2100 duplexer for EU/US WCDMA operations. Furthermore, if the bands overlap in frequency (e.g. 1800 and 1900 bands), the diplexer approach is equally impossible. In those cases, switching is currently the only option.
Due to the large number of different bands and the number of combinations thereof in different systems used around the world, using traditional methods and topologies for band selection and mode switching is difficult. Currently, there are many regional variants in the band combinations that may be implemented for different regions in the world. Some of these variants are listed below:
US1: 4xGSM (850, 900, 1800, 1900) & 2xUS-WCDMA (850, 1900)
US2: 4xGSM (850, 900, 1800, 1900) & 2xUS-WCDMA (1700/2100, 1900)
EU1: 4xGSM (850, 900, 1800, 1900) & EU-WCDMA (2100)
EU2: 4xGSM (850, 900, 1800, 1900) & EU-WCDMA (1800, 2100)
EU/US: 4xGSM (850, 900, 1800, 1900) & EU-WCDMA (2100) & US-WCDMA (1900)
It would be difficult to implement all these different variants efficiently if the GSM and WCDMA modes are handled separately and no switching is used for WCDMA.
It should be noted that the 850 frequency band and the 1900 frequency band can be used in any one of GSM, WCDMA and CDMA standards. For example, the 850 GSM in the US2, EU1, EU2 and EU/US variants can also be used for CDMA or WCDMA instead. Likewise, the 1900 GSM in the EU1, EU2 variants can also be used for CDMA or WCDMA.
The nomenclature of the bands and the respective Rx/Tx frequencies are listed in Table I.
TABLE IContinentNameTX freqRX freqUSGSM 850824–849869–894EUGSM 900880–915925–960EUGSM 18001710–17851805–1880USGSM 19001850–19101930–1990USWCDMA or CDMA 850824–849869–894USWCDMA or CDMA 19001850–19101930–1990USWCDMA 1700/21001710–17552110–2155EUWCDMA 18001710–17851805–1880EUWCDMA 21001920–19802110–2170
It is thus advantageous and desirable to provide a method to optimize the mobile phone engine variants and front-end architecture.